The present invention relates generally to systems and methods for disposal of materials containing toxic metals, and more particularly to system and method for disposal of plastic media blasting materials containing toxic metals from paint stripping operations.
Solid wastes produced by stripping paint from painted surfaces may be classified by the Environmental Protection Agency (EPA) as hazardous under the Resource Conservation and Recovery Act (RCRA) because of excessive concentrations of toxic metals in the paint pigments. The procedure recommended by the EPA for treating waste containing hazardous concentrations of metals includes chemical stabilization and solidification of the waste. However, because paint stripping waste characteristically contains only small amounts of metal (about 1 wt %), the balance being organic paint polymer (vehicle) and paint stripping medium, solidification and stabilization of untreated waste costs about 100 times more than necessary based on metal content alone. When a plastic medium is used to strip paint, the bulk of the waste is organic which may be incinerated but for the accompanying release of airborn metal vapor or particulate matter, which release to the environment is undesirable.
The invention provides system and method for disposing of paint stripping waste generated from a plastic media blasting (PMB) process or other organic waste containing excessive concentrations of toxic metals according to RCRA, wherein the waste is reduced in volume by controlled heating at temperatures high enough to oxidize the organic portion of the waste but low enough to avoid vaporization of the metal compounds in the paint pigments followed by stabilization of the resulting ash (principally metal oxides) into a cementitious compact. Laboratory tests on the method show that a 95% or greater reduction of waste volume may be achieved, which may reduce solidification and stabilization costs by a factor of 20 or more. No detectable toxic metal vapors or particulates are released to the atmosphere during the process.
It is therefore a principal object of the invention to provide system and method for treating organic material containing toxic metals.
It is a further object of the invention to provide system and method for low temperature ashing of plastic or other organic waste containing hazardous concentrations of toxic metals.
It is a further object of the invention to provide system and method for disposal of plastic blasting media waste from paint stripping operations.
It is a further object of the invention to provide system and method for weight and volume reduction of paint stripping waste.
It is another object of the invention to provide system and method for stabilization and disposal of hazardous metals contained in paint stripping or other organic waste.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.